Vibration damping materials are used to prevent vibration or noise of various structures to insure sustained quietude. The vibration damping materials have been widely used for, for example, underfloor spaces of automobile interior, or for railway vehicles, ships, aircrafts, electric devices, buildings, or construction machinery. Such vibration damping materials have been conventionally made from materials having vibration absorbing performance or sound absorbing performance, and molded products such as plate products or sheet products have been used as vibration damping materials. Such molded products are however difficult to use at vibration- or noise-generation positions having complicated shapes. Therefore, various methods for improving the workability and maintaining sufficient vibration damping property have been examined. For example, an inorganic powder-containing asphalt sheet has been used for underfloor spaces of automobile interior. However, since the sheet must be bonded by thermal fusion, the workability and the like need to be improved. Therefore, studies have been made on various compositions or polymers for forming vibration damping materials.
Application type vibration damping materials (coating materials) have been developed as an alternative to such molded products. For example, vibration damping coating materials have been suggested which can absorb vibration or sound in the form of a coating formed by spraying a vibration damping coating material onto or applying a vibration damping coating material to target areas by an optional method. Specifically, aqueous vibration damping coating materials with improved coating hardness have been developed, which are obtained by blending a vehicle such as asphalt, rubber, or synthetic resin with synthetic resin powders. In addition, for interior parts of automobiles, vibration damping coating materials have been developed, which are prepared by dispersing activated carbon as a filler into a resin emulsion. However, these conventional items still do not reach the sufficient level of vibration damping performance. Therefore, a technique for achieving sufficient vibration damping performance has been required.
As conventional compositions or the like used for vibration damping materials, for example, Patent Literature 1 discloses a copolymer emulsion for vibration damping materials prepared by copolymerizing a monomer mixture essentially including an acrylic monomer.